Plaster of Paris casts have been in use to immobilize body members or limbs for some time. The plaster of Paris bandages have been supplemented and, to some extent, superseded by synthetic cast tapes or bandages which employ polymeric materials on a substrate. The preferred polymeric materials are water-cured or water-reactive polyurethane compositions. The polyurethane materials have largely supplanted other polymeric synthetic casting materials. These polyurethane casting materials are of the type which are disclosed in U.S. Pat. No. 4,376,438, U.S. Pat. No. 4,411,262, and U.S. Pat. No. 4,433,680.
The fibrous substrate used in the synthetic casting materials is usually a polyester or fiberglass. Although knitted substrates are most common, woven substrates have also been used. The fiberglass materials offer advantages in terms of strength of the finished cast and various constructions of fiberglass fabrics have been used for the substrates for the synthetic casting tapes. U.S. Pat. Nos. 3,686,725, 3,787,272 and 3,882,857 disclose specific fiberglass materials, or the treatment of fiberglass yarns, to produce fiberglass substrates which are particularly suitable for use in orthopedic casts.
U.S. Pat. No. 4,323,061 discloses a cast substrate made from a combination of glass fibers and a second fiber such as cotton, flax, rayon, wool, acrylic resin, nylon, Teflon or polyester. The purpose of the second fiber in the substrate is to hold the curable resin on the substrate.
Casting tapes with improved conformability combine extensible and nonextensible yarns in the tape substrate are disclosed in U.S. Pat. Nos. 4,668,563; 4,940,047; 5,027,804; 5,256,134; 5,382,466; and 5,403,267.
U.S. Pat. Nos. 4,667,661 and 4,774,937 and 4,937,146 disclose the use of various lubricious materials as additives to the water hardenable materials used in casting tapes to reduce the tackiness of the water hardenable polyurethane resins and allow easier molding of the casting tape to the limbs of the patient. Also disclosed is the modification of the water hardenable prepolymer itself to provide lubricating effects. These lubricious materials interfere to some extent with the lamination of the successive layers of the casting tape to one another when the cast is applied to the patient. Inadequate lamination can result in finished casts with less than the desired strength characteristics.
U.S. Pat. Nos. 5,061,555 and 5,180,632 disclose casting tapes in which the prepolymer contains a hydrophilic bisureathane as a detackifying agent.